How different reality often is from flame wars, particularly when the subject is legal.

The Software Freedom Law Center has just announced that it
"has carefully reviewed the lineage of the open source Atheros wireless
driver for Linux and determined which portions can be distributed
under the ISC license (also known as the 2-clause BSD license)" [the full analysis is here]:

The licensing situation for the Atheros driver is complex because much
of it was originally derived from an OpenBSD project called ar5k. This
original code is licensed under the ISC license, but Linux code is
typically licensed under the GNU General Public License (GPL). The GPL
places specific additional requirements on distributors of software to
ensure that its users are able to obtain the software's source code,
and freely to copy, modify, and redistribute all subsequent modified
versions.

Ultimately, all the copyright holders of the Linux ath5k-driver code,
derived from ar5k, have been contacted and have agreed to license
their changes under the ISC license, thus allowing improvements to be
re-incorporated into OpenBSD. One of the three historical branches of
the code reviewed by SFLC, however, included portions that are only
licensed under the GPL, and SFLC has determined that it would be very
difficult to re-incorporate that code into OpenBSD.

So now you know why it took a while to get an answer. They were contacting all the authors. So much for hotheads. SFLC also released some guidance for developers who wish to incorporate code with a permissive license into a GPL program. Here it is. There is specific information on how to preserve copyright notices in a project that already uses a file-by-file approach instead of one single copyright file, as most GPL software does it, and there is a paper on what is and isn't copyrightable. And going forward, there is advice regarding dual licensing.

They analyze it from both perspectives, as the goal is to avoid confusion. For those who want a permissive license:

Common attempts by developers at stating dual license notices tend to be confusing, contradictory, and legally unclear. While there may be cases where it will make sense for a developer (with a knowledgeable lawyer’s assistance) to place a dual license on his code, we generally recommend that developers not use dual licensing if their goal is simply to allow recipients to use the code within larger GPL’d works as well as under permissive terms. If such a developer is using a license like the modified BSD license or the ISC license, where there is an established and widespread community understanding that the terms permit incorporation into larger programs covered by the GPL, the developer should simply use the permissive license without any further reference to the GPL.

If you do want to use the GPL and yet wish to incorporate code under a permissive license, there is a step by step guide on how to get it right:

One of the most challenging licensing policies to implement is one in which permissive terms are retained on files within a larger GPL’d work. This section presents procedures that should be followed by GPL’d projects that desire to maintain a subset of the codebase under permissive terms. These procedures will help such projects ensure that their work complies with all applicable licensing requirements while preserving collaborative relationships with partner projects working on permissive-licensed code.

As for what is sufficient to warrant a copyright notice, the advice is to be cautious and assume a copyright notice is legitimate:

Not every modification to a program is copyrightable by the person making the modification. Minor edits are sometimes too small or insufficiently original to give rise to a copyright interest. If a contributor has only made formatting changes or has only contributed non-expressive data, such as constant values, it is possible that the contributor holds no copyright in the work.

Most of the time, however, patches submitted to a project are sufficient to create a copyright interest. Most countries have adopted a very low standard of originality and creativity for copyrighted works, and even a few lines of code or the rearrangement of different sections of a project might be enough to cause the contributor to be a copyright holder. Because there is no way to know for certain whether a court in a given jurisdiction would find a particular contribution copyrightable, it is most prudent to assume that there is a copyright in the contribution. Such prudence is justified by a consideration of the legal consequences of error. If a notice of an invalid copyright is placed on the program, the copyright notice has no legal effect. If, on the other hand, notice of a valid copyright is omitted, there may be disastrous consequences if the contributor later objects to the use of the material contrary to the contributor’s license. For these reasons, every contributor to a given work should be listed in the copyright notice, and all contributors should be consulted when projects contemplate relicensing. Even if some contributions appear to be too minor or non-creative to be copyrightable, the project should consult with a copyright lawyer before determining that the contributor need not be consulted in a relicensing decision.

I haven't finished reading and analyzing it myself, so we can do it together.
Here's the meat of the press release:

NEW YORK, September 27, 2007 -- The Software Freedom Law Center
(SFLC), provider of pro-bono legal services to protect and advance
Free and Open Source Software (FOSS), today announced that it has
carefully reviewed the lineage of the open source Atheros wireless
driver for Linux and determined which portions can be distributed
under the ISC license (also known as the 2-clause BSD license).

The licensing situation for the Atheros driver is complex because much
of it was originally derived from an OpenBSD project called ar5k. This
original code is licensed under the ISC license, but Linux code is
typically licensed under the GNU General Public License (GPL). The GPL
places specific additional requirements on distributors of software to
ensure that its users are able to obtain the software's source code,
and freely to copy, modify, and redistribute all subsequent modified
versions.

Ultimately, all the copyright holders of the Linux ath5k-driver code,
derived from ar5k, have been contacted and have agreed to license
their changes under the ISC license, thus allowing improvements to be
re-incorporated into OpenBSD. One of the three historical branches of
the code reviewed by SFLC, however, included portions that are only
licensed under the GPL, and SFLC has determined that it would be very
difficult to re-incorporate that code into OpenBSD.

To share its knowledge with the FOSS and legal communities and to
share background regarding its analysis, SFLC today has also released
two documents of general interest. One document is a set of guidelines
for developers who wish to incorporate code with a permissive license,
such as ISC, into a GPL-licensed project. The other paper discusses
the legal standards of originality with regard to computer programs
under U.S. and international copyright law.

The two general papers, as well as a detailed document explaining
SFLC's review of the Linux Wireless team's ath5k driver, are available
at http://www.softwarefreedom.org/resources/

"We're pleased to help bring clarity to the Linux Wireless Developers
as they work towards inclusion of their code in the Linux kernel,"
said Karen Sandler, SFLC Counsel.

This is not the first time that SFLC has worked with the Linux
Wireless developers. In July, SFLC announced that it had performed a
confidential audit of the open source Atheros driver and determined
that no portion of it was illegally copied from Atheros' proprietary
code.